Our goals in this application are to understand the signaling events in the cell that control the endocytosis and genome delivery of influenza virus. Our rationale is that an understanding of the fundamental molecular events involved in the entry of influenza viruses into cells will be critical for the development of future antiviral drugs, designed to combat both the annual epidemics of influenza virus infection in the human population, as well as pandemic influenza. We have three specific aims: 1 - To investigate cellular signaling responses during influenza virus endocytosis. One of the major goals of this application is to understand the regulatory mechanisms underlying the route of influenza virus entry into cells. The initial focus of this project is to understand how influenza virus communicates with the signaling network of the cell. Activation of cellular signaling pathways by influenza virus has previously been studied at late times of infection;however critical signaling events occurring during influenza virus entry remain unexplored. 2 - To investigate the clathrin and non-clathrin routes of influenza virus entry and the role of the actin cytoskeleton. We have previously shown that influenza virus can efficiently enter cells in the absence of clathrin-mediated endocytosis. In contrast to the situation with clathrin- and caveolae-mediated endocytosis, there is a relative paucity of information on alternative routes of entry. The major goals of this section are to characterize the non-clathrin, non-caveolae route of influenza entry, and to integrate our knowledge of both clathrin- and non-clathrin endocytosis in polarized epithelial cells. 3 - To investigate the upstream signaling events during influenza entry that are required for influenza virus internalization. Our goal in this aim is to understand the specific interactions that occur at the cell surface to coordinate endocytic trafficking and signaling during influenza virus entry. Influenza is a major public health problem worldwide. In the United States, the virus is responsible for over 36,000 deaths annually, with the possibility of emergence of new and potentially deadly strains of the virus. As such, it is classed as an NIAID category C priority pathogen for biodefense and emerging infectious disease research. We believe our work will provide a framework for the basic understanding of influenza virus entry and lead to the development of new anti-viral drugs, which are still necessary to combat this potentially devastating viral disease.